1. Field of the Invention
The invention relates in general to a filtering device and a filtering method and a semiconductor fabricating method thereof, and more particularly to a filtering device with an adsorbing element having a plurality of surface-increasing elements arranged in a direction parallel and a filtering method and a semiconductor fabricating method thereof.
2. Description of the Related Art
During the semi-conductor manufacturing process, the wafer must go through several steps of manufacturing processes to complete various micro-electronic elements and the layout of circuits. No matter the manufacturing process is deposition process, oxidation process, diffusion process or etching process, it is possible that exhaust gas mixed with particles is generated in the semi-conductor machine.
The semi-conductor machine has a reaction chamber and an exhaust pipe. The thin-film deposition process of the wafer is processed at a reaction chamber, and the exhaust gas generated during the manufacturing process is extracted from reaction chamber through the exhaust pipe. Especially, for those low-pressure deposition processes, such as plasma enhanced chemical vapor deposition (PECVD) or low pressure chemical vapor deposition (LPCVD), the exhaust gas must be extracted from the reaction chamber through the exhaust pipe by a pump. The pump, when started, can extract the gas from the reaction chamber through the exhaust pipe so that the reaction chamber is void of exhaust gas, or maintain the reaction chamber at a low-pressure or a vacuum state.
The gas in the reaction chamber is normally mixed with particles such as silicon nitride. The particles can be attached to the inner-wall of the exhaust pipe, affecting extraction, or enter the pump, resulting in overload. Therefore, a cold trap is needed to filter the gas.
A conventional cold trap is used for filtering particles in the gas. The temperature of the gas is higher than the temperature of the cold trap. The conventional cold trap includes a cooling space and a cylindrical cooling element. With the extraction of the gas by the pump, the gas can enter the cooling space through the exhaust pipe at one end of the cooling space and leave the cooling space from another end of the cooling space to enter the pump. The cylindrical cooling element is disposed within the cooling space, and the temperature of the cylindrical cooling element is lower than the temperature of the gas entering the cooling space. When the gas contacts the surface of the cylindrical cooling element in the cooling space, the temperature of the gas plummets. Therefore, part of the particles will be absorbed to the surface of the cylindrical cooling element. By doing so, the cold trap can filter particles in the gas, lest the particles be attached to the inner-wall of the exhaust pipe or the pump.
However, the surface of the cylindrical cooling element is smooth and has a limited absorptive area, so that the absorption of particles in the gas by the cylindrical cooling element is restricted. The absorptive capacity of the cylindrical cooling element will soon reach a saturation state, and can not continue to absorb particles in the gas. Therefore, the operator needs to halt the operation of the machinery and replace or clean the cylindrical cooling element. Thus, too short a replacement cycle of the cylindrical cooling element not only reduces the productivity of the facility and increase labor costs, but also increases the danger of replacing the cylindrical cooling element.